The present invention relates to an RF (Radio Frequency) pulse applying method and an MRI (Magnetic Resonance Imaging) apparatus, and more specifically to an RF pulse applying method and an MRI apparatus capable of receiving a signal of tissue long in T2 at a relatively high level and suppressing artifacts.
There has heretofore been known a pulse sequence of Balanced SSFP (Steady-State Free Precession) wherein a pulse train for increasing a flip angle is inserted before the application of an imaging pulse (refer to, for example, a patent document 1).
There has further been proposed a pulse sequence for suppressing artifacts at Balanced SSFP (refer to, for example, a non-patent document 1).
[Patent Document 1] Japanese Unexamined Patent Publication No. 2004-329268 (claim 1 and FIG. 3)
[Non-Patent Document 1] D. L. Foxall “Starter Sequence for Steady-State Free Precession Imaging” Magnetic Resonance in Medicine 53:919-929 (2005)
Generally, at Balanced SSFP, a signal of tissue long in T2 is relatively high in a state of transition (Transient State) to a Steady-state and becomes low in the Steady-state.
Since a transient state is long in the prior art described in the patent document 1, a signal of tissue long in T2 can be received at a relatively high level and contract can be kept high by performing data acquisition in the transient state.
However, a problem arises in that artifacts such as “Banding Artifact”, etc. occur due to variations in the signal in the transient state.
On the other hand, the prior art described in the non-patent document 1 restricts variations in the signal in the transient state and suppresses the artifacts.
However, the present prior art is accompanied by problems that since the steady-state is formed quickly and the transient state is short, the signal of tissue long in T2 is hard to receive at a relatively high level and contract cannot be set high.